| Abstrakt: |
Study objective – The aim was to determine the receptors involved in the antiaggregatory effects of adrenaline in the rat.Design – The 111indium oxine technique was used to evaluate ADP induced pulmonary accumulation of 111In labelled platelets in adrenalectomised rats (ie, no endogenous adrenaline) in the absence of anticoagulants. Adrenaline was infused (10, 20 and 40 μg·kg−1·h−1) and ADP aggregation measured. Adrenoceptor agonists, isoprenaline, methoxamine, and BHT 933, were given to evaluate whether they mimic the adrenaline effects. Adrenoceptor antagonists, yohimbine, propranolol, prazosin, and WY 26392, were given to assess whether they block the adrenaline effects.Measurements and main results – In all cases, pulmonary accumulation of platelets was measured in response to ADP. Adrenaline dose dependently inhibited platelet aggregation. BHT 933 (1.5 μg·kg−1·min−1) mimicked, while phentolamine (1 mg·kg−1), yohimbine (2.5 mg·kg−1), and WY 26392 (0.1, 1.0, 5.0 mg·kg−1) blocked, the adrenaline effects. Methoxamine (3.3 μg·kg−1·min−1) produced a relatively weak non-specific inhibition of ADP aggregation. Isoprenaline (33 ng·kg−1·min−1) did not mimic the effects of adrenaline, neither did propranolol (1 mg·kg−1) affect the adrenaline inhibition of the aggregatory responses to ADP. Indomethacin (3 mg·kg−1) blocked the inhibitory effects of adrenaline.Conclusions – Adrenaline stimulates α receptors on platelets but inhibits platelet aggregation. There is no evidence to suggest that β receptors participated in the effects produced by adrenaline. There is a role for cyclo-oxygenase products in the inhibitory effects of adrenaline on aggregation. [ABSTRACT FROM PUBLISHER] |
